#include <stdio.h>
#include <stdlib.h>
#include <string.h>



#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>


void error_handling(char *message);


int main(int argc, char *argv[])
{
    int serv_sock;
    int clnt_sock;

    struct sockaddr_in serv_addr;
    struct sockaddr_in clnt_addr;
    socklen_t clnt_addr_size;

    char message[] = "Hello World!";

    if ( argc != 2) {
        printf("Usage: %s <port> \n", argv[0]);
        exit(1);
    }

    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if ( serv_sock == -1) {
        error_handling("socket() error");
    }
    // INADDR_ANY: get address auto
    memset(&serv_addr, 0, sizeof( serv_addr) );
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(atoi(argv[1]));

    if (bind(serv_sock, &serv_addr, sizeof(serv_addr)) == -1) {
        error_handling("bind() error");
    }

    if ( listen(serv_sock, 5) == -1) {
        error_handling("listen() error");
    }

    clnt_addr_size = sizeof(clnt_addr);
    clnt_sock = accept(serv_sock, (struct sockaddr *) &clnt_addr, &clnt_addr_size);
    if (clnt_sock == -1) {
        error_handling("accept() error");
    }

    write(clnt_sock, message, sizeof(message));
    close(clnt_sock);
    close(serv_sock);



    return 0;
}


void error_handling(char *msg)
{
    fputs(msg, stderr);
    fputc('\n',stderr);
    exit(1);
}